SAN FRANCISCO INTERNATIONAL FILM FESTIVAL By coincidence there were two Bigfoot movies at the Sundance Film Festival this year, and both are also playing this year's SFIFF. One was long and serious: Christopher Munch's Letters from the Big Man, a fantasy drama eco-parable in which a Forest Service water analyst scouting remote parklands acquires a very hairy stalker — though he means well. The other was only five minutes and not remotely serious: Sasquatch Birth Journal 2 (it's unclear whether there was ever a first), which provided hidden-camera proof of the species' existence, caught in a state of universal discomfort.

That was the latest dose of absurdism from Zellner Bros., who weren't strangers to Sundance (they've had other shorts and the 2008 feature Goliath premiere there), but remain little-known to all but a small coterie of fans outside their home base of Austin, Texas. That situation will be somewhat rectified with "From A to Zellner," which brings the brothers to SF for a program of short works.

Considering that they've been making films for at least 15 years (and home movies before that), Nathan and David Zellner are something of a mystery pair. Their website bio reveals that "they were born in Greely, Colorado" — and nothing else. (It does, however, provide photographic evidence of them wearing matching, flared-pant crimson jumpsuits somewhere around third grade, and a video where they sing the theme to 1984's The Neverending Story with tone-deaf bravado.)

Elsewhere David has said he "typically tackles more of the writing-directing, and Nathan more of the editing and producing. That said, it all overlaps." They've occasionally acted in friends' movies, including ones by mumblecore biggies Andrew Bujalski and the Duplass brothers, plus 2000's epically great, virtually unknown underground Road Warrior-Smokey and the Bandit collision Radio Free Steve. That aside, far be it from us to further spoil the enigma by requesting an interview.

At their best, the Zellners are like Beckett meets Upright Citizens Brigade, or something like that. Existential rudderlessness almost invariably slaps already hapless protagonists in the face like a wet trout, amid distressed circumstances of deadpan ridiculousness.

Sometimes the humor is overly juvenile or the joke just doesn't stretch far enough. But their commitment to strange ideas — abetted by considerable flexibility as comic actors inhabiting different characters, accents, mustaches — is more often refreshing, distinctive, and delightful.

Shorts that might show up Sunday, April 24 include Redemptitude (2006), a Australian priest-vs.-angry-wheelchair-bound paintballer confrontation that upends sagas of inspirational forgiveness; the next year's Aftermath on Meadowlark Lane, a hilariously inappropriate debate (just after a possibly fatal car crash) on the circumcision question; 2004's The Virile Man, in which husband and father Gary (David) literally calls from the closet to whisper sexual-identity fears to an astrology hotline. Then there's 2005's Foxy and the Weight of the World, in which David's Irish ne'er-do-well Hamish, poisoned by a "vengeful rival," pours out bitterly self-pitying wisdoms to a beloved pet that would clearly rather be anywhere else than clutched in his dying arms.

The Zellners have made three features to date, all relatively obscure but fairly easy to find on Amazon and such. The aforementioned Goliath is about a rather pathetic recent divorcee (David) distraught when his beloved cat vanishes — something he irrationally blames on the way more pathetic local registered sex offender (Nathan). The brothers are excellent but their material just doesn't have the weight to float its darker tonal shifts.